Acceleration-responsive switch

ABSTRACT

An acceleration switch comprised of a housing having an internal cylindrical bore of at least two different diameters. A mass is adapted to move longitudinally within the smaller diameter bore into the larger diameter bore under excessive acceleration forces and thereby cause a compressed spring contact to expand so as to form an electrical contact bridge. This will alert the user that the switch was subjected to excessive forces.

United States Patent Inventor Leonard P. Tetrault Northport, N.Y.

Appl. No. 825,838

Filed Mar. 19, 1969 Patented Jan. 4, 1972 Assignee Aerodyne ControlsCorporation Farmingdale, N.Y.

ACCELERATION-RESPONSIV E SWITCH 10 Claims, 4 Drawing Figs.

US. Cl 200/6153 Int. Cl H01h 35/14 Field of Search ZOO/61.45,

References Cited UNITED STATES PATENTS 3,337,701 8/1967 PrebilicZOO/61.45 3,022,393 2/1962 Weaver ZOO/61.45

Primary Examiner-Robert K. Schaefer Assistant Examiner-M. GinsburgAttarney-Edward H. Loveman ABSTRACT: An acceleration switch comprised ofa housing having an internal cylindrical bore of at least two differentdiameters. A mass is adapted to move longitudinally within the smallerdiameter bore into the larger diameter bore under excessive accelerationforces and thereby cause a compressed spring contact to expand so as toform an electrical contact bridge. This will alert the user that theswitch was subjected to excessive forces.

memmm 4m 3632.920

2351 HA0 W Q Q INVENTOR LEONARD P. TETRAULT ATTORNEYACCELERATlON-RESPONSIVE SWITCH This invention relates to an indicatordevice and, more particularly, to an improved and novel device formeasuring the forces of shock, impact or acceleration. The inventionespecially discloses a unique miniaturized acceleration-responsiveswitch which is extremely simple in construction and which may beinexpensively manufactured.

In industry and numerous fields of technology, accelerationresponsiveswitches or devices are widely employed for measuring or sensingcontinuous or maximum acceleration forces. For certain applications,only maximum acceleration forces need be known, since this particularinformation discloses whether or not predetermined tolerances of shockor vibration have been exceeded, with the likelihood of damage havingbeen sustained by the apparatus or component subjected to such forces.In particular, this type of maximum acceleration measurement becomes ofgreat significance and importance in the evaluation of a aircraft orspace technology components, or in connection with the shipment or useof delicate instruments or other fragile articles. Althoughacceleration-responsive switches for sensing and measuring the maximumacceleration, shock or impact forces encountered, are presently in use,these have been and are of a generally complex and cumbersomeconstruction, are not sufficiently precise in their acceleration sensingcharacteristics, and furthermore, are not particularly economical tomanufacture.

The acceleration-responsive switch according to the present inventionobviates the disadvantages and drawbacks encountered in the prior art byproviding a device of extremely simple and inexpensive constructionwhich will readily indicate whether the apparatus or component to whichit is attached has been subjected to acceleration forces, shock orimpact beyond allowable tolerances. Accordingly, the present inventioncontemplates the provision of an electrical nonconductive housing havinginternal cylindrical bores of at least two different diameters. Amovable cylindrical mass or slug is longitudinally slidable within thesmaller diameter bore, and has a compressed spring contact positioned ina groove extending about the periphery of the movable mass. When theswitch is subjected to an axial acceleration force beyond apredetermined level or tolerance, the mass will slide toward the borehaving an enlarged diametral dimension whereby the compressed springcontact will radially expand or snap outwardly into the enlarged portionof the bore so as to bridgingly contact a pair of spaced electricalcontacts positioned in the enlarged bore portion. This, in effect, willplace the contacts in an electrically conductive relationship and permittheir connection to an electrical circuit for testing if the circuit hasbeen closed by the excessive acceleration force or shock. Suitablespring means and electrically nonconductive damping fluids may beprovided within the bore in order to control the acceleration-responsivecharacteristics of the movable mass.

Accordingly, it is a primary object of the present invention to providefor a novel and improved acceleration-responsive indicator deviceadapted to measure and sense maximum acceleration forces along apredetermined sensing axis.

Another object of the present invention is to provide for a novelacceleration switch incorporating a movable mass adapted to close anelectrical circuit when the maximum acceleration, shock or impactexceeds an allowable tolerance level.

A further object of the present invention is to provide an improvedacceleration switch including a movable sliding mass having anexpandable metallic member which is adapted to form an electrical bridgebetween two electrical contact points when the acceleration forces onthe switch exceed allowable tolerance levels.

These and other objects and many of the attendant advantages of thisinvention will be readily appreciated as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, in which;

FIG. 1 is a longitudinal cross-sectional view of one embodiment of thedevice according to the present invention;

FIG. 2 is a sectional view along line 2-2 in FIG. 1;

FIG. 3 is a sectional view along line 3-3 in FIG. I; and

FIG. 4 is a longitudinal cross-sectional view of a second embodiment ofthe device according to the present invention.

Referring now to the drawings, wherein like reference charactersdesignate like or corresponding parts throughout the several views, inFIGS. 1 to 3 there is illustrated an acceleration-responsive switch,generally designated as reference numeral I0. The switch I0 includes acasing or housing 12, preferably formed of a plastic material. Thehousing 12 has a generally cylindrical bore 14 which has an enlargeddiametrical end portion 16. A closure member 18 is adapted to seal thebore 14 at bore end 16 while the other end of bore 14 is sealed off by ahousing end wall 20.

A generally cylindrical mass or slug 22 is positioned within bore 14 andadapted to slide therealong in a freely moving relationship. Aperipheral groove 24 in cylindrical mass 22 contains an expandableresilient spring contact 26 which normally presses radially outwardlyagainst the surface of bore 14. The spring contact 26 may bemanufactured of any electrically conductive spring material and in itsrelaxed position resembles a split ring with a gap between the splitends. When the contact 26 and the mass 22 are positioned within the bore14, the spring contact 26 may be compressed such that the gap betweenthe split ends is vertically nonexistent. The cylindrical mass 22 isnormally retained in bore 14 adjacent to housing end wall 20 by means ofa compression spring 28 which extends between an inner flange 30 oncylindrical mass 22 and shoulder 31 on closure member 18.

A pair of arcuate, spaced electrical contact shoes 32, 34 are positionedin enlarged bore portion 16, and are sandwiched between housing 12 andclosure member 18 so that the radially inner surfaces 36, 38 of contactshoes 32, 34 form a bore somewhat larger than bore 14. Electrical wires40, 42 are each fastened by welding, brazing, or other conventionalwellknown means, to respective contact shoes 32, 34 and extend throughsealed apertures 44, 46 in housing 12.

The interior of housing 12 may then be filled with a fluid havingelectrically nonconductive properties through a threaded aperture 48 inclosure member 18. The aperture 48 may then be closed by means of ascrew 50, and the entire assembly or switch 10 sealed through theapplication of a suitable plastic sealant.

In operation, one or more switches 10 may be positioned in a shippingcarton containing delicate instruments. If the carton is subjected toacceleration forces, shocks or impacts beyond an allowable toleranceduring shipment, the acceleration force applied to cylindrical mass 22against spring 28 will be sufficient to compress the latter and permitmass 22 to slide along bore 14 toward enlarged bore end I6. As may bereadily evident, the acceleration force tolerance required to causemovement of mass 22 along bore 14 is determined by the force ofcompression spring 28 against the mass 22. The viscosity of the fluid inhousing 12 will determine the response characteristics of the switch 10.

As the groove 24 on the periphery of mass 22 reaches the enlarged boreportion 16 the compressed resilient spring contact 26 will snap ordeflect radially outwardly until it contacts the surfaces 36, 38 onelectrical contact shoes 32, 34, whereby the spring contact 26 forms anelectrical conduit or bridge between contact shoes 32, 34. Thus, whenthe instruments are unpacked at their shipping destination points, it isa simple matter to serially connect wires 40, 42 of a switch 10 to aconventional audio or visual electrically powered alarm. If the switch10 had been subjected to acceleration forces or shocks of magnitudeswhereby the spring contact 26 formed an electrical bridge with contactshoes 32, 34, the alarm will be electrically energized. This indicatesthat the shipped instruments or components sustained shock oracceleration beyond the allowable tolerance. Conversely, if the ring 26is still within its groove 24 in contact with the surface of bore 14,the alarm will not be energized indicating that the instruments were notsubjected to excessive acceleration forces, shock or impact.

The fluid within housing 12 acts primarily as a damping fluid. As themass 22 moves toward bore end 16, the fluid located in the bore portionbetween the mass 22 and closure member 18 is allowed to pass through anaperture 52 in mass 22 toward the housing end wall 20. By varying theviscosity of the fluid, devices having different acceleration-responsivecharacteristics may be produced without extensive manufacturingmodifications.

The second embodiment of the invention illustrated in FIG. 4 of thedrawings is generally similar in principle of operation to that of thedevice in FIG. 1. However, whereas the switch in FIG. 1 is designed sothat mass 22 moves along bore 14 in one direction, the device accordingto this embodiment can more in either one of two coaxial directions. Inthis instance, the switching device 60 includes a housing 62 having acylindrical bore 64. Each end of bore 64 extends into a diametricallyenlarged bore portion 66, 68, each containing a pair of spaced arcuateelectrical contact shoes 32, 34. The housing 62 is sealed at one end byits end wall 70, and at its other end by closure member 18 seated inbore portion 66.

A cylindrical mass 72 is freely slidable within bore 64 and balancedlongitudinally centrally thereof by a pair of opposed compressionsprings 28, 74 which are positioned about respective shoulders 31 and76. The outer peripheral surface of mass 72 contains a pair of spacedgrooves 78, 80, each containing a resilient spring contact 26 compressedwithin bore 64. As in the embodiment of FIG. 1, the interior of housing62 is filled with an electrically nonconductive fluid which can freelypass through aperture 82 in mass 72 upon movement of the latter alongbore 64. 7

Each of the contact shoes'32'and contact shoes 34 are interconnectedrespectively by wires 40, 42 passing through sealed apertures 84, 86 inhousing 62. The entire assembly is sealed against fluid leakage by meansof a suitable plastic sealant.

During operation, as the switch 60 is subjected to anacceleration-force, shock or impact of sufficient intensity to move mass72 along bore 64 in either axial direction, that is,

' toward closure member 18 or toward housing end wali 70, one

of the compressed contact springs 26 will snap outwardly either in boreportion 66 or bore portion 68. This will cause the extended springcontact 26 to form an electrical bridge between its connected set ofcontact shoes 32, 34. Accordingly, this particular embodiment affordsmeasurement of bidirectional shock loads or acceleration forces and thusin- I creases the versatility of the switch device.

Although the invention has been described as being used with alarmcircuits, it is obvious that the output signal from the electricalbridge may be used for detonating an explosive charge, opening a door,etc. Moreover, if desired, the housing 12 may be manufactured of atransparent material such as an 1 acrylic plastic whereby the positionof the contact springs in the enlarged bore portion may be visuallyobserved.

It will now appear that in accordance with the objects, a uniqueacceleration switch has been disclosed which will indicate that it hasbeen actuated even if the mass 22 is returned to its original positionwith the bore portion 14.

The foregoing disclosure relates to only a preferred embodiment of theinvention, and is intended to cover all changes and modifications of theexample of the invention. herein chosen for the purposes of disclosure,which do not constitute depar- Y spaced electrical contact meanspositioned within said enlarged bore portion,

said movable cylindrical mass including at least a peripheral groove,and

a spring contact means positioned in said peripheral groove,

whereby said cylindrical mass, in response to said predeterminedacceleration, will move toward said diametrically enlarged portion ofsaid bore such that said peripheral groove enters said diametricallyenlarged portion thereby permitting said spring contact means toradially expand so as to form an electrical contact bridge between saidspaced electrical contact means.

2. A switch as defined in claim 1 further including a damping meanslocated in said bore and adapted to control the acceleration response ofsaid cylindrical mass.

3. A switch as defined in claim 1 wherein said spaced electrical contactmeans comprise a pair of arcuate electrical contact shoes,

and a pair of electrical wires extending through said housing, each ofsaid wires being connected respectively to, one of said contact shoes,said wires being adapted to be connected to an electrically poweredalarm.

4. A switch as defined in claim 1 wherein said housing includes an endwall which closes off one end of said bore and a closure mounted on saidhousing to close off the other end of said bore.

5. A switch as defined in claim 4, further including a resilient biasingmeans positioned in said bore,

said biasing means normally maintaining said movable cylindrical mass inaxially spaced relationship from said enlarged end portion of said bore.

6. A switch as defined in claim 5 wherein said resilient biasing meanscomprises a compression spring member.

7. A switch as defined in claim 1 wherein each end of said bore includesan enlarged diameter portion,

a pair of spaced electrical contact means being positioned in each ofsaid enlarged diameter portions,

said cylindrical mass having a peripheral groove adjacent each endthereof, and

a pair of spring contact means each one of said spring contact meansbeing positioned respectively in each of said grooves, whereby movementof said cylindrical mass toward either end of said bore in response to apredetermined acceleration, causes said spring contact means adjacentsaid bore end, to radially expand into the enlarged diameter portion soas to form an electrical contact bridge between the spaced electricalcontact means in said enlarged diameter portion.

8. A switch as defined in claim 7 including a damping fluid in said boreto control the acceleration response of said cylindrical mass.

9. An acceleration switch comprising:

a housing having a generally cylindrical bore extending longitudinallytherein and an end wall which closes off one end of said bore, saidhousing being manufactured of a transparent material,

a closure member mounted on said housing so as to close the other end ofsaid bore,

a generally cylindrical mass being disposed within said bore with radialclearance for movement along the longitudinal axis of said bore inresponse to a predetermined acceleration having at least a componentalong said axis,

said bore having a diametrically enlarged portion at one end thereof,

a resilient biasing means positioned in said bore and adapted tonormally maintain said cylindrical mass in axially spaced relationshipfrom said enlarged end of said bore,

said cylindrical mass including at least a peripheral groove thereon,and

an expandable spring contact means positioned in said peripheral grooveand compressed to fit within said bore whereby said cylindrical mass inresponse to said said cylindrical mass having a peripheral grooveadjacent each end thereof, and wherein said expandable spring contactmeans comprise. a pair of spring contact means, each of said springcontact means being positioned respectively in each of said grooves.

1. An acceleration switch comprising; a housing having a generallycylindrical bore extending longitudinally therein, a generallycylindrical mass being disposed within said bore with radial clearancefor movement along the longitudinal axis of said bore in response to apredetermined acceleration having at least a component along said axis,said bore having a diametrically enlarged portion at least at one endthereof, spaced electrical contact means positioned within said enlargedbore portion, said movable cylindrical mass including at least aperipheral groove, and a spring contact means positioned in saidperipheral groove, whereby said cylindrical mass, in response to saidpredetermined acceleration, will move toward said diametrically enlargedportion of said bore such that said peripheral groove enters saiddiametrically enlarged portion thereby permitting said spring contactmeans to radially expand so as to form an electrical contact bridgebetween said spaced electrical contact means.
 2. A switch as defined inclaim 1 further including a damping means located in said bore andadapted to control the acceleration response of said cylindrical mass.3. A switch as defined in claim 1 wherein said spaced electrical contactmeans comprise a pair of arcuate electrical contact shoes, and a pair ofelectrical wires extending through said housing, each of said wiresbeing connected respectively to, one of said contact shoes, said wiresbeing adapted to be connected to an electrically powered alarm.
 4. Aswitch as defined in claim 1 wherein said housing includes an end wallwhich closes off one end of said bore and a closure member mounted onsaid housing to close off the other end of said bore.
 5. A switch asdefined in claim 4, further including a resilient biasing meanspositioned in said bore, said biasing means normally maintaining saidmovable cylindrical mass in axially spaced relationship from saidenlarged end portion of said bore.
 6. A switch as defined in claim 5wherein said resilient biasing means comprises a compression springmember.
 7. A switch as defined in claim 1 wherein each end of said boreincludes an enlarged diameter portion, a pair of spaced electricalcontact means being positioned in each of said enlarged diameterportions, said cylindrical mass having a peripheral groove adjacent eachend thereof, and a pair of spring contact means each one of said springcontact means being positioned respectively in each of said grooves,whereby movement of said cylindrical mass toward either end of said borein response to a predetermined acceleration, causes said spring contactmeans adjacent said bore end, to radially expand into the enlargeddiameter portion so as to form an electrical contact bridge between thespaced electrical contact means in said enlarged diameter portion.
 8. Aswitch as defined in claim 7 including a damping fluid in said bore tocontrOl the acceleration response of said cylindrical mass.
 9. Anacceleration switch comprising; a housing having a generally cylindricalbore extending longitudinally therein and an end wall which closes offone end of said bore, said housing being manufactured of a transparentmaterial, a closure member mounted on said housing so as to close theother end of said bore, a generally cylindrical mass being disposedwithin said bore with radial clearance for movement along thelongitudinal axis of said bore in response to a predeterminedacceleration having at least a component along said axis, said borehaving a diametrically enlarged portion at one end thereof, a resilientbiasing means positioned in said bore and adapted to normally maintainsaid cylindrical mass in axially spaced relationship from said enlargedend of said bore, said cylindrical mass including at least a peripheralgroove thereon, and an expandable spring contact means positioned insaid peripheral groove and compressed to fit within said bore wherebysaid cylindrical mass in response to said predetermined accelerationwill move toward said diametrically enlarged portion of said bore suchthat said peripheral groove enters said diametrically enlarged portionthereby permitting said spring contact means to radially expand and bevisible through said transparent housing.
 10. A switch as defined inclaim 9 wherein each end of said bore includes a diametrically enlargedportion, said cylindrical mass having a peripheral groove adjacent eachend thereof, and wherein said expandable spring contact means comprise,a pair of spring contact means, each of said spring contact means beingpositioned respectively in each of said grooves.